It is commonly recognized that extensive research program is vital to enhance the understanding of low-dose radiation effects on biological systems from cells to humans. Rigorous research is needed to reduce uncertainties associated with the effects of low-dose radiation exposures. Low-dose exposure conditions arise from high natural background areas, occupational radiation exposure, diagnostic radiology, space travel and, undesired low-dose exposure during cancer radiotherapy. The low-dose radiation exposure conditions may be broadly categorized as, first, relatively very protracted low doses from natural sources and second, man-made radiation low-dose exposure to public/nuclear workers and patients. Though the situations of natural background radiation are beyond our control, but we accept to live with it inherently and naturally. However, the low-dose radiation exposures associated with diagnosis/therapy are becoming unavoidable to public owing to wide acceptability due to overweighing medical benefits. There is a growing increase in the use of X-rays, and computed tomography (CT) scans to diagnose many infectious and noninfectious diseases in both developed as well in developing countries. Such diagnostic interventions have not only saved millions of lives but also helped in developing rationale-based therapy for many ailments. However, the public perception and scientific opinions among radiation biologists differ related to risk associated with low-dose radiation exposures. It may be important to mention here that as low as reasonably achievable (ALARA), principle is very strictly followed while deciding the permissible dose limits in case of man-made radiation sources by the national and international regulating agencies.

While intense discussions on low-dose radiation affect issues at various national/international platforms, questions have been raised mainly about diagnostic and occupational radiation exposures. The increased risk of cancer incidence during X-rays and CT scans in diagnostic procedures has been discussed.[1],[2],[3] A typical dose to the lung from a conventional chest X-ray could range from 0.01 mGy to 0.15 mGy while the doses to an organ examined with a conventional CT may vary from 10 mGy to 20 mGy or even may be as high as 80 mGy in coronary angiography procedure. However, there are contradictory opinions from another school of researchers who advocate for reduced the cancer risk during CT scans.[4]

It is however to be noted that estimation of risk after low-dose exposure is based on the results available from A-bomb survivors of Hiroshima, where the low-dose risk estimate is mainly derived from the extrapolation using linear no-threshold (LNT) model. LNT model believes that the unit increase in radiation risk is valid even at the lowest doses similar to what follows at high doses. On the contrary, some scientists believe that LNT model is not valid for the risk associated with low doses, and instead of linearity, a “J” shaped risk curve persists for very low to low-dose regimen (<100 mGy). There is no doubt that like any other genotoxic agent, radiation too has a probability of producing harmful effects beyond certain doses. However, the real risk of low-dose radiation effects remains inconclusive despite significant efforts due to uncertainties in measurement in biological end points. On the other hand, the LNT model of radiation risk continues to guide for setting the safety standards for public and radiation professionals. Therefore, health effect concerns to low-radiation doses continue under the background of radiation fear/phobia in the mind of general public. In this context, it is the onus of radiobiologists and radiation health scientists to address the issues unequivocally. Indeed, for this purpose, well-designed research strategies need to be conducted using various cellular and molecular biological approaches at low-dose ranges based on the epidemiological studies on the human population. It is undoubtedly true that manifestation of biological consequences after radiation exposure involves multiple complex processes of interaction of radiation with living systems. However, with the use of appropriate end points, refined methods and newer molecular tools/kits, it is hoped to become possible to unravel and quantify subtler radiation responses of biological systems helpful in evaluating the risk of low-dose radiation exposure.